Mule.
These effects are the same as were produced by the bobbin and fly-frame, but in the throstle they are attained by simpler means. In the former machine a distinct movement caused the bobbin to revolve quicker than the spindle. In the throstle the bobbin is made to revolve by the pull of the yarn, which is now sufficiently strong for the purpose; but the roving in the bobbin-and-fly frame would not bear the strain. The throstle is not often employed for very fine spinning, because fine yarn would not bear the drag of the bobbin; but in mule-spinning the yarn is wound at once upon the spindles without any strain. In the mule the rolling is first drawn by the usual system of rollers, and then stretched by a moveable carriage. The effect of first drawing and then stretching is to make the yarn finer and more uniform, as will be explained presently. The spinning mule is the most interesting and impressive spectacle in a large cotton mill—on account of its vast extent, the great quantity of work performed by it, and the wonderful complication and ingenuity of its parts.
The spinning-mule consists of two principal portions: the first, which is fixed, contains the bobbins of rovings and the drawing rollers; the second is a sort of carriage, moving upon an iron railroad, and capable of being drawn out to a distance of about five feet from the fixed frame. This carriage carries the spindles, the number of which is half that of the bobbins of rovings. Motion is given to the spindles by means of vertical drums, round which are passed slender cords, communicating with the spindles. There is one drum to every twenty-four spindles.
The carriage being run up to the point from which it starts in spinning, the spindles are near to the roller-beam; the rollers now begin to turn, and to give out yarn, which is immediately twisted by the revolution of the spindles; the carriage then moves away from the roller-beam, somewhat quicker than the threads are delivered, so that they receive a certain amount of stretching, which gives value to this machine. The beneficial effect is produced in this way,—when the thread leaves the rollers, it is thicker in some parts than in others, and those thicker parts not being so much twisted as the thinner ones are softer, and yield to the stretching power of the mule, so that the twist is equalised throughout, and the yarn becomes more uniform. When the carriage has completed a stretch, or is drawn out from about fifty-four to sixty-four inches from the roller-beam, the drawing rollers cease to give out yarn, but the spindles continue to whirl until the threads are properly twisted. In spinning the finer yarns, the carriage sometimes makes what is called a second stretch, during which the spindles are made to revolve much more rapidly than before. The drawing, stretching, and twisting, of a length of thread being thus completed, the mule disengages itself from the parts of the machinery by which it has hitherto been driven, and the spinner then pushes the carriage with his knee back to the roller-beam, turning at the same time with his right hand a fly wheel, which gives motion to the spindles. At the same time a copping wire, as it is called, is pressed upon the threads by the spinners’ left hand, and they are thus made to traverse the whole length of the spindle, upon which they are then wound or built in a conical form, which is called a cop. These cops are used for placing in the shuttle in weaving, and form the weft or short cross threads of the cloth.
Machinery for moving Shuttle. Shuttle for Power Loom.
The yarn is now disposed of in various ways, according to the use for which it is intended; but it is often found convenient to make it up into hanks. When the yarn is completed it is usually sent to the doubling and twisting mill, for the purpose of being converted into what is now properly called thread. Although we are accustomed to apply the word thread to a thin narrow line of any fibrous material, the manufacturer limits the term to that compound cord produced by doubling or twisting two or more single lines. The single line he calls yarn, two or more single lines, laid parallel and twisted together, he calls thread; and of this there are many varieties, such as bobbin-net-lace-thread, stocking-thread, sewing-thread, &c.
Gassing.